This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions comprised of coated carrier components, or coated carrier particles that can be prepared by, for example, dry powder processes, and wherein the coating is a polymer containing an antimony tin oxide. More specifically, the present invention relates to compositions, especially carrier compositions comprised of a core, and thereover at least one polyme,r and dispersed therein and thereon antimony tin oxide of a suitable average size, such as from about 15 to about 45 nanometers, and more specifically, from about 16 to about 32 nanometers. In one form, the antimony tin oxide (ATO) possesses a more negative potential than a number of carbon blacks, and thus may not cause a reduction in negative tribo as is the situation with carbon black; and the nanometer size of the ATO ensures sufficient surface area of this filler and thus sufficient conductivity at similar volume percent loadings as carbon black. Also, in one form the ATO is light gray in color and in a powder form, thereby resulting in minimal contamination when color toners are generated and used for development.
In embodiments of the present invention, the carrier particles are comprised of a core with a coating thereover of a polymer, such as a polymethylmethacrylate (PMMA) and the like; polyvinylidenefluoride, polyethylene, copolyethylene vinylacetate, copolyvinylidenefluoride tetrafluoroethylene, polystyrene, polytetrafluoroethylene, polyvinylchloride, polyvinylfluoride, polylbutylacrylate, copolybutylacrylate methacrylate, polytrifluoroethyl methacrylate, polyurethanes, and mixtures thereof, especially a mixture of any two of these polymers, copolymers of methylmethacrylate and dimethylaminoethyl methacrylate, methylmethacrylate copolymers with substituted alkyl aminoethyl methacrylate, butylaminoethyl methacrylate, polyvinylidenefluoride and polymethylmethacrylate, and the like, and which polymer coating contains ATO. The carrier may include the polymer coating thereover in admixture with other suitable polymers, and more specifically, with a second polymer, such as a fluoropolymer, polymethylmethacrylate, poly(urethane), especially a crosslinked polyurethane, such as a poly(urethane)polyester, and the like; and moreover, the copolymer coating contains in place of a conductive component, such as a suitable carbon black, ATO of nanometer size, and which ATO component is dispersed in and on or in the polymer coating. With the ATO conductive component, there can be enabled carriers with increased developer triboelectric response at relative humidities of from about 20 to about 90 percent improved image quality performance, excellent high conductivity ranges of from about 10−10 to about 10−7 (ohm-cm)−1, and the like. A specific advantage associated with the carriers of the present invention with the polymer coatings thereover include a high triboelectrical charge (measured as charge to diameter ratio in nanocoulombs per meter), for example the carrier can provide toners with a tribocharge of from about a minus (negative charge) 0.1 to about 10, or to about 7 nanocoulombs per meter, and more specifically, from about a negative 0.2 to about a negative 4 nanocoulombs per meter, and yet most specifically, from about a negative 0.4 to about a negative 2 nanocoulombs per meter.
The carrier particles of the present invention can be selected for a number of different imaging systems and devices, such as xerographic copiers and printers, inclusive of high speed color xerographic systems, printers, digital systems, combination of xerographic and digital systems, and wherein colored images with excellent and substantially no background deposits are achievable. Developer compositions comprised of the carrier particles illustrated herein and prepared, for example, by a dry coating process are generally useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes. Additionally, the invention developer compositions comprised of substantially conductive carrier particles are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the toner triboelectric charge with the carrier particles can be preselected, which charge is dependent, for example, on the polymer composition and dispersant component applied to the carrier core, and optionally the type and amount of the conductive component selected.